config: remove AC_PROG_CC as it overrides AC_PROG_C_C99

XORG_STRICT_OPTION from XORG_DEFAULT_OPTIONS calls
AC_PROG_C_C99. This sets gcc with -std=gnu99.
If AC_PROG_CC macro is called afterwards, it resets CC to gcc.

Signed-off-by: Gaetan Nadon <memsize@videotron.ca>

configure.ac

@@ -36,7 +36,6 @@ XORG_DEFAULT_OPTIONS
 AM_CONFIG_HEADER(config.h)
 
 # Check for progs
-AC_PROG_CC
 AC_PROG_LIBTOOL
 
 # Check for dependencies